Nanolatex technology 2: blending polymer nanoparticles with conventional latexes for synergistic property improvement

• Published in: Journal of Coatings Technology and Research 2021-07, Vol.18 (4), p.1165-1176
• Main Authors: Jones, Frank N., Joshi, Ravi G., Provder, Theodore, Shen, Weidian
• Format: Article
• Language: English
• Subjects: Chemistry and Materials Science; Corrosion and Coatings; Industrial Chemistry/Chemical Engineering; Materials Science; Polymer Sciences; Surfaces and Interfaces; Thin Films; Tribology
• ISSN: 1547-0091; 1935-3804
• DOI: 10.1007/s11998-021-00474-0

Results of our research on crosslinked latexes and polymer nanoparticles will be reported. Goals of this long-term program have been: comparing precoalescence and post-coalescence crosslinking; synthesizing polymer nanoparticle latexes (~ 20 to 25 nm) from a variety of acrylic monomers, including crosslinking and crosslinkable monomers; and blending nanoparticle latexes with compatible conventional (~ 120 to 130 nm) latexes and understanding their effects on film formation and on fundamental and empirical film properties. As we previously reported, blending conventional and nanolatexes in an 85/15 ratio (w/w of polymer solids) effects substantial changes of fundamental film properties. Best results included reducing minimum filming temperatures (MFT) while increasing Young’s moduli by factors of two to 17. Substantial improvements in empirical film properties such as gloss (up to 97 at 60°), hardness (increased by 2–5 pencils), block resistance, and adhesion to aluminum were also found. The previous report covered only a single blend ratio. Here we report studies of blends with ratios of conventional to nanoparticle latexes ranging from 92.5/7.5 to 30/70 (w/w). As before, the latexes and nanolatexes are BMA/BA copolymers with 0–4 wt.% of 1,3-butylene glycol dimethacrylate (precoalescence crosslinker) and 0–5 wt.% of diacetone acrylamide (for post-coalescence crosslinking with adipic dihydrazide). Films cast from these blends are subjected to everyday empirical coatings tests and are characterized using instrumental tests including dynamic mechanical analysis (DMA) and modulated differential scanning calorimetry (MDSC). Film formation and film morphology are studied using atomic force microscopy (AFM). The results confirm that blending nanoparticles at ratios up to 50/50 (w/w of polymer solids) can substantially improve certain properties of conventional latex films. For many properties, the optimum ratio is around 85/15 conventional/nano; a 92.5/7.5 ratio also affords substantial improvements. As coatings, the blends have near-zero VOC.